Armstrong EvaPack™ Series converts ordinary tap water to water vapor using an adiabatic process. Dry air passes through a corrugated bank of wetted cells media made from non-organic wet fibers. The EvaPack™ uses the sensible air heat to evaporate the water, cooling and humidifying the air with low energy consumption and minimal pressure drop. It is highly suitable for air handling units, duct applications, and data center environmental control where precise temperature and relative humidity management is critical.

How the EVAPACK™ Series Works

Adiabatic Process

Usually, there are two typical psychrometric design processes for evaporative humidification:

• Heating + humidification: The pad efficiency is smaller, and its thickness is thinner.
• Pre-heating + humidification + post heating: The pad efficiency is higher, and its thickness is bigger.

Both processes have a humidity ratio (Δx) increase. The Saturation Efficiency (ŋ) or Cooling Efficiency is expressed in % and corresponds to the ratio between the entering dry bulb temperature and exiting dry bulb temperature over the wet bulb depression.

Features and Benefits

• Plug and Humidify: Water connections are on the side for quick, simple installation. Compact design with a maximum footprint of 24" (600 mm). Works with potable water, reverse osmosis (RO), or soft water.
• Low and Easy Maintenance: Cassettes are accessible by the side or front. Water pump, level detector, and manual gate valves are on the service side.
• Customized Design: Tailor-made sizing from approximately 3.9 ft² (0.36 m²) to 96.8 ft² (9.00 m²) in a one-piece assembly. Multiple humidifiers can be combined for larger sections.
• Efficient: Uses the heat present in the air for humidifying and cooling. Optimized water contact surface provides up to 12% more area than traditional evaporative pads.

Configurations and Components

Direct Water Configuration (DW)

Recommended with high hardness supplied water (to increase the pad life time) or with reverse osmosis water (to reduce the RO water consumption).

Operation Sequence:

1. Water enters from the water supply and arrives at the dispersion manifold. The flow is adjusted with a manual gate valve.
2. Calibrated orifices deliver the water evenly over each media pad.
3. Dry air passes through the wetted cells media, cooling and humidifying the air.
4. Excess water washes the evaporative pad and is eliminated (with minerals) from the water basin through the draining connection.

Recirculated Water Configuration (RW)

Recommended when the available supplied water has a low or medium hardness.

Operation Sequence:

1. Water enters the basin passing through the filling valve. The water level sensor controls basin filling and pump start-up.
2. The recirculation water pump supplies water to the dispersion manifolds.
3. Dry air passes through the wetted cells media, cooling and humidifying the air.
4. Excess water washes the pad and falls back into the water tank.
5. Excess minerals are drained by the draining valve, minimizing water consumption and media scaling.

EvaPack™ Evaporative Pad

The EvaPack™ evaporative pad is an inorganic pad made of fiberglass sheets.

• High degree of wetting: Special impregnated glass fibre material ensures continuous humidification.
• Rigid: Corrugated and compact structure with no rigidity loss and no fiber loss in the air flow.
• Safe: Contains no harmful substances. Complies with RoHS 2011/65/UE.
• Hygienic: Fulfills the requirements of VDI 6022, Part 1 (04/2006) for microbial inertness.
• Fireproof: Non-combustible Euro Class "A1" according to EN ISO 1716:2011 and UNE EN ISO 1182:2011. UL Certified Standard 900 for air filters.

WARNING

The EvaPack™ evaporative pad material should not be cut or crushed as doing so may generate dust. This product is non-hazardous under ordinary conditions of use.

Installation Requirements

• The humidifier must be installed horizontally. Use a spirit level to ensure the unit is level front to back and across the width.
• Non-corrosive blanking plates must be installed to prevent air bypass around the unit in the AHU.
• Supply air units must have at least two filter stages (first stage min. ePM1 ≥ 50% or F7 filter). The humidifier must be placed in-between the filter stages.

DANGER

The dry bulb temperature and the wet bulb temperature of the inlet air must be positive to avoid water freezing on the pad.

VDI 6022 Hygienic Requirements

• All non-metallic products used for installation must not absorb moisture or provide a nutrient substrate for micro-organisms.
• The relative humidity downstream from the humidifier section must not exceed 90%.
• Drainage system must be equipped with a siphon with a non-return valve or a siphon disconnected from the sewage network.
• In case of shutdown or failure of the ventilating system, the humidifier shall be switched off automatically.

Maintenance and Water Quality

EvaPack™ can work with potable water, reverse osmosis, or softened water. Water quality must comply with local regulations.

TIP

To prevent microorganism development (bacteria, algae, fungi), the EvaPack™ must be emptied and dried when not used for more than 24 hours.

Bleed-off and Scale Prevention

Water usually has a high percentage of minerals. The evaporative mechanism leaves mineral deposits on the pad.

• For RW units: Bleed-off is managed through water draining valve settings.
• For DW units: Bleed-off is managed through an excess of water flow.

The bleed-off must be set according to the water quality. The Puckorius Saturation Index (PSI) is recommended to determine the Concentration Cycle Number (COC). When bleed-off water flow is more than 1.5 times the evaporated water (COC < 1.66), DW configuration is strictly recommended.